Description: A beam of light shines through a tank of water and sodium thiosulfate and onto the side wall. Add a small amount of acid to the water and stir with the stick. The "sun" will begin to turn orange. The scattering will increase until even the reds no longer pass through the tank.

Instructions: Add 10ml of sodium thiosulfate for each 500 ml of water before the demonstration. When ready for the reaction to start, add 3-8ml of either hydrochloric or sulfuric acid for each 500 ml of water. In about a minute (depending on the temperature of the solution), colloidal sulfur will begin to form and the beam passing through the liquid will look bright blue by scattered light. The solution should be room temperature for best results.